1. Technical Field:
This invention relates to a method of merging head suspension assemblies into disk drives using a low melting wax. In particular, the invention relates to an improved method for protecting sliders and disks during handling while storing, shipping and assembling disk drives. The invention also relates to an improved slider which is embedded in wax.
2. Description of the Related Art:
In a disk drive or direct access storage device, the disk files are information storage devices which utilize at least one rotatable disk storing information on concentric data tracks. A transducer reads information from or writes information to the various tracks on the data disk. The transducer forms a portion of a "head" which is attached to a slider, forming the head. The slider is attached on its backside to the suspension. The suspension in turn is connected to the actuator arm. The actuator arm positions and maintains the head over the desired track during read and write operations. These parts are assembled into the actuator.
In a traditional disk drive, the rotation of the disk creates a cushion of air over the disk that allows the slider to lift off and float over the disk. The actuator arm suspension provides dimensional stability between the slider and the actuator arm by compensating for the force of the air between the slider's air bearing surface and the disk surface. The suspension controls slider flexibility relative to its directions of motion while resisting out-of-plane movement. This action keeps the slider close to the disk surface without allowing contact between them.
The suspension typically comprises a load beam attached to the actuator arm and a flexure which connects the slider to the load beam. The load beam balances the slider by counteracting the lifting force from the spinning disk. The flexure supports the slider and allows flexibility during the slider's ride on the cushion of air. Such a suspension is described in U.S. Pat. No. 4,167,765, which is assigned to the same assignee as this application.
In a disk drive using a self-replenishment, lubrication system, a liquid lubricant replaces the cushion of air. The sliders do not float above the disk in this system, but ski in the liquid. These sliders glide in a lubricant during track following, like a water skier gliding in a thin layer of water at high speed. There are several milliliters of lubricant in such a disk drive.
Assembly of disk drives is labor intensive. Parts are often manufactured and tested in one place and assembled in another. For instance, a slider may be machined, tested and attached to the suspension assembly to form the head suspension assembly, then boxed for shipment. Any damage makes the head suspension assembly unusable, thereby wasting the part.
Damaged sliders are serious problems in the industry. Sliders are usually made of a hard brittle material, such as a ceramic. If the slider is subjected to a shock, such as dropping or hitting, the slider may crack, chip or break. For example, if the slider of the head suspension assembly has small bearing pads, any damage such as chipping removes a large percentage of the slider bearings and causes an irregular surface. If a chipped slider touches the disk, the hard surface scratches and destroys the disk. The same type of damage occurs with other slider surfaces, for example, rails, grooves, and other textured surfaces. Another situation where damage occurs is when the actuator is handled harshly during shipment. In some circumstances, the actuator holds eight pairs of opposing heads. If the actuator is roughly handled, the heads may hit each other, a phenomenon known as head slap. Simply setting the actuator's shipping container down too hard can cause head slap. Head slap causes chips, dents, cracks, and the like, rendering the heads unusable.
In the case of air bearing sliders, the prior art uses mechanical fixtures to protect the sliders. However, head slap still occurs occasionally due to operator error.
Near contact recording disk drives have very small spaces between the disks. A disk stacking tolerance allows the greatest possible number of disks stacked without wasting any space. This tight tolerance accommodates the worst case scenario, allowing parts to hit without being damaged. The tight tolerance must accommodate back-to-back sliders, arms, spacer rings and the like, all of which vary slightly after manufacture. For the slider, no more than three standard deviations from the mean of the slider size are allowed. For example, a 0.45 mm thick slider allows deviations of no more than a mere 0.05 mm in its thickness. Consequently, merging the slider with the disk is a tight squeeze without much room for error.
Merging the sliders between the disks requires careful manipulation. During merge, the small, fragile heads must squeeze between the delicate disks without touching. If the heads and disks touch, the pressure from contact can damage both heads and disks, thereby rendering them unusable. The same types of problems can occur when moving the head to the landing zone. If the slider touches the disk during movement to the landing zone, and a hard particle of contaminant becomes wedged between the slider and disk the slider can scrape the disk like a needle scrapes a phonograph record. The scraping may scratch and ruin the disk.
One object of the invention is to protect the head suspension assemblies from damage during shipment and handling.
Another object of the invention is to ease the merge operation between the head and the disk during assembly.
Another object of the invention is to guard the head and disk from damage during merge and positioning the head on the landing zone.